1. Field of the Invention
The present invention relates to a vehicle transmission in which a group of parts including at least an input gear and an output gear are stacked and supported on a shaft supported in a casing via at least a pair of bearings, and a torque that has been input to the input gear is output from the output gear.
2. Description of the Related Art
Assembled around a main shaft or a counter shaft of an automatic transmission in order to establish each of the gear shift stages are parts including, for example, a gear, a clutch outer and a clutch inner of a hydraulic clutch for engaging the gear with the shaft, and bearings for supporting the shaft in a casing. Such a plurality of parts are stacked on the shaft, the parts are retained at one end by a step formed on the shaft, and are retained at the other end by means of a nut screwed into the outer circumference of the shaft, as disclosed in Japanese Patent Application Laid-open No. 11-82646.
In an automatic transmission, the use of helical gears is preferred, because of their low engagement noise. A helical gear is characterized by receiving a thrust force accompanying the transmission of a torque. When two helical gears supported on a shaft experience thrust forces that are generated in opposite directions, not only is it necessary to secure the helical gears to the shaft by a large nut or bolt that can withstand the thrust forces, but it is also necessary to employ means for preventing the nut or bolt from loosening.
The present invention has been carried out in view of the above-mentioned circumstances and it is an object of the present invention to eliminate the necessity of fixing helical gears supported on a shaft of a transmission by a nut or a bolt in the axial direction, thus saving space and reducing the number of parts.
In order to achieve the above-mentioned object, the present invention is directed to a vehicle transmission in which a group of parts including at least an input gear and an output gear are stacked and supported on a shaft supported in casings via at least one pair of bearings and a torque that has been input to the input gear is output from the output gear, wherein the input gear and the output gear are helical gears, thrust forces acting on the input gear and the output gear are generated in opposite directions, the thrust force acting on one gear is borne by the casing via a shaft end of the shaft, and the thrust force acting on another gear is borne by the casing via a side of the gear.
In accordance with the above-mentioned arrangement, the input gear and the output gear supported on the shaft are helical gears, and when they experience the thrust forces in opposite directions, the thrust force acting on the one gear is borne by the casing via the shaft end, and the thrust force acting on the other gear is borne by the casing via the side of the gear. It is therefore unnecessary to fix the two gears to the shaft by a bolt or a nut and to employ means for preventing the bolt or nut from loosening. Space can thus be saved and the number of parts can be reduced.
The present invention is also directed to a vehicle transmission wherein a retaining part provided integrally on the shaft restricts movement of the one gear in the direction in which the one gear departs from the other gear, and a retaining means detachably provided on the shaft restricts movement of the other gear in the direction in which the other gear departs from the one gear.
In accordance with the above-mentioned arrangement, because the retaining part provided integrally on the shaft restricts movement of the one gear in the direction in which the one gear departs from the other gear, the thrust force acting on the one gear can be transmitted to the shaft and borne by the casing. Moreover, because the retaining means detachably provided on the shaft restricts movement of the other gear in the direction in which the other gear departs from the one gear, it is possible to provisionally assemble the other gear on the shaft while preventing the other gear and the group of parts from dropping off the shaft, thus enhancing ease of assembly.
A torque converter case 11 and a transmission case 12 in the embodiment below correspond to the casings of the present invention, a sub-shaft drive fourth gear 34 in the embodiment corresponds to the input gear or the one gear of the present invention, a second sub third speed gear 46 in the embodiment corresponds to the output gear or the other gear of the present invention, a ball bearing 20, a roller bearing 21 and a thrust bearing 69 in the embodiment correspond to the bearings of the present invention, a second sub-shaft Ss2 in the embodiment corresponds to the shaft of the present invention, an annular projection 61 in the embodiment corresponds to the retaining part of the present invention, and a cotter 67 in the embodiment corresponds to the retaining means of the present invention.